Distribution of stellar masses of the 44 ALPINE [C II]-detected nonmerger galaxies at z = 4.4 − 5.9 (red histogram) and the comparison sample of 101 CO-detected MS SFGs at 1 <  z <  3.7 compiled from the literature (gray histogram). The solid and dashed lines correspond, respectively, to the medians and means of the two distributions. The black thick lines show the range and the mean of M_stars of the A³COSMOS galaxies at 1 <  z <  6 (Liu et al. 2019b). Clearly, the ALPINE sample probes a much lower M_stars range than previous galaxy samples with molecular gas mass measurements obtained mostly at lower redshift.